Question

If injury causes the CPP to fall outside the range between _______ mm Hg, the brain loses its ability to autoregulate and CBF becomes directly dependent on MAP for perfusion.

Answer 1

When the cerebral perfusion pressure falls outside the range of approximately 70 to 100 mm Hg, the brain cannot autoregulate its blood flow, making it dependent on mean arterial pressure, which should be above 60 mm Hg to prevent ischemia and hypoxia.

Step-by-step explanation:

If injury causes the cerebral perfusion pressure (CPP) to fall outside the range between approximately 70 to 100 mm Hg, the brain loses its ability to autoregulate, and cerebral blood flow (CBF) becomes directly dependent on mean arterial pressure (MAP) for perfusion. Under normal circumstances, CPP can maintain adequate blood flow by autoregulation. However, deviations from normality can lead to significant problems. For example, when the MAP falls below 60 mm Hg for an extended period, blood pressure may not be sufficient to ensure circulation through the tissues, leading to ischemia or insufficient blood flow. Ischemia can result in hypoxia, a state of inadequate oxygenation of tissues, which can be particularly damaging to neurons that are highly sensitive to oxygen levels.